Health Insurance and Differences in Infant Mortality Rates in the US

IMPORTANCE: Health insurance status is associated with differences in access to health care and health outcomes. Therefore, maternal health insurance type may be associated with differences in infant outcomes in the US. OBJECTIVE: To determine whether, among infants born in the US, maternal private insurance compared with public Medicaid insurance is associated with a lower infant mortality rate (IMR). DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from the Centers for Disease Control and Prevention (CDC) Wide-Ranging Online Data for Epidemiologic Research expanded linked birth and infant death records database from 2017 to 2020. Hospital-born infants from 20 to 42 weeks of gestational age were included if the mother had either private or Medicaid insurance. Infants with congenital anomalies, those without a recorded method of payment, and those without either private insurance or Medicaid were excluded. Data analysis was performed from June 2022 to August 2023. EXPOSURES: Private vs Medicaid insurance. MAIN OUTCOMES AND MEASURES: The primary outcome was the IMR. Negative-binomial regression adjusted for race, sex, multiple birth, any maternal pregnancy risk factors (as defined by the CDC), education level, and tobacco use was used to determine the difference in IMR between private and Medicaid insurance. The χ(2) or Fisher exact test was used to compare differences in categorical variables between groups. RESULTS: Of the 13 562 625 infants included (6 631 735 girls [48.9%]), 7 327 339 mothers (54.0%) had private insurance and 6 235 286 (46.0%) were insured by Medicaid. Infants born to mothers with private insurance had a lower IMR compared with infants born to those with Medicaid (2.75 vs 5.30 deaths per 1000 live births; adjusted relative risk [aRR], 0.81; 95% CI, 0.69-0.95; P = .009). Those with private insurance had a significantly lower risk of postneonatal mortality (0.81 vs 2.41 deaths per 1000 births; aRR, 0.57; 95% CI, 0.47-0.68; P < .001), low birth weight (aRR, 0.90; 95% CI, 0.85-0.94; P < .001), vaginal breech delivery (aRR, 0.80; 95% CI, 0.67-0.96; P = .02), and preterm birth (aRR, 0.92; 95% CI, 0.88-0.97; P = .002) and a higher probability of first trimester prenatal care (aRR, 1.24; 95% CI, 1.21-1.27; P < .001) compared with those with Medicaid. CONCLUSIONS AND RELEVANCE: In this cohort study, maternal Medicaid insurance was associated with increased risk of infant mortality at the population level in the US. Novel strategies are needed to improve access to care, quality of care, and outcomes among women and infants enrolled in Medicaid.